The emerging advances in adjuvant therapies for malignant bone and soft tissue tumors and the introduction of a surgical staging system to rationalize the extent and margin of tissue resection have renewed the interest in limb-saving procedures. The use of prosthetic implants based on the most advance biomechanical design concepts and new implant materials appears to be very promising, not only to provide useful limb function for curable cancer patients but also as a palliative treatment to benefit those with metastatic lesions. Two systems of metallic tumor prostheses were developed, but our clinical and laboratory results have demonstrated significant residual problems associated with these devices. Therefore, the currently proposed renewal is to achieve the following specific aims: 1) to develop a new non-porous coated modular tumor prosthetic system; 2) to modify the previous porous-coated modular prosthetic system and to examine the efficacy of extra-cortical fixation through bony ingrowth; 3) to investigate the adjuvant therapy effects on tissue incorporation into the porous implant; 4) to develop a method to attach soft tissue to the prostheis; 5) to correlate patients' clinical assessment results with their biomechanical functional evaluation results; and 6) to develop booklets for better patient home care and to write instructional manuals describing surgical techniques involving these protheses. Bone geometric study and theoretical and experimental stress analyses will be performed to optimize the design of the modular systems. Dogs will be used as the models to investigate the biological, functional and adjuvant therapy effects on prosthesis fixation through radiographic, histologic and biomechanical analyses of the specimens. Established objective functional evaluation methods and techniques will be used to study the patient's functions and correlate them with the clinical assessment criteria proposed by Dr. W. Enneking. We plan to initiate a multi-institutional trial program after the new prosthetic systems are developed and tested. The long-term objective is to perfect two segmental bone/joint prosthetic systems which can be safely used on the majority of the patients with resectable primary tumors for restoration of function and those with metastatic lesions for palliative purposes. These devices can also be used effectively in general orthopedic surgery for limb salvage in the treatment of trauma, infection, metabolic bone disease or failed joint arthroplasty cases with extensive bone loss.